alt, 65 feet in thickness, was reached at
a depth of 1,127 feet. Other reasons induced the owners of the
Clarence iron works to continue the bore hole for 150 feet below the
bed of salt; a depth of 1,342 feet from the surface was then reached.
During the process of boring, considerable quantities of inflammable
gas were met with, which, on the application of flame, took fire at
the surface of the water in the bore hole. The origin of this gas, in
connection with the coal measures underlying the magnesian limestone,
will probably hereafter be investigated.

For raising the salt, recourse was had to the method of solution, the
principle being that a column of descending water should raise the
brine nearly as far as the differences of specific gravity between the
two liquids permitted--in the present case about 997 feet. In other
words, a column of fresh water of 1,200 feet brought the brine to
within 203 feet of the surface. For the practical application of this
system a hole of say 12 inches in diameter at the surface was
commenced, and a succession of wrought iron tubes put down as the
boring proceeded, the pipes being of gradually decreasing diameter,
until the bottom of the salt bed was reached. The portion of this
outer or retaining tube, where it passed through the bed of salt, was
pierced with two sets of apertures, the upper edge of the higher set
coinciding with the top of the seam, and the other set occupying the
lower portion of the tube. Within the tube so arranged, and secured at
its lower extremity by means of a cavity sunk in the limestone, a
second tube was lowered, having an outer diameter from two to four
inches less than the interior diameter of the first tube. The latter
served for pumping the brine. The pump used was of the ordinary bucket
and clack type, but, in addition, at the surface, there was a plunger,
which served to force the brine into an air vessel for the purposes of
distribution. The bucket and clack were placed some feet below the
point to which the brine was raised by the column of fresh water
descending in the annulus formed between the two tubes. In commencing
work, water was let down the annulus until the cavity formed in the
salt became sufficiently large to admit of a few hours' pumping of
concentrated brine. On the machinery being set in motion, the stronger
brine was first drawn, which, from its greater specific gravity,
occupied the lower portion of the cavity. As the brine was